Buying appetite is waning as more traders are drawn into the market on days in which stocks end lower rather than participating in rallies. On-Balance Volume or OBV was invented in the 1960s using volume as an indicator of market pressures. It’s pretty straight forward: on up days, volume gets added and on down days, volume gets subtracted. While the magnitude of the moves doesn’t matter, the direction and volume are key, and so is divergence from price trends.